1. Technical Field
The present invention relates to a radiographic imaging apparatus, which is used in an X-ray imaging apparatus for medical use or the like.
2. Related Art
FPD's (Flat Panel Detectors) that have a radiation sensitive layer disposed on a thin film transistor (TFT) active matrix substrate, detect irradiated radiation, such as X-rays, and directly convert this radiation into radiographic image data expressing the distribution of irradiated radiation amounts are being put into practice. Portable radiographic imaging apparatuses (sometimes referred to below as “electronic cassettes”) that house a panel type radiation detector, such as one of the FPDs, a control section including a memory section, and a power source section, also being put into practice for storing in the image memory radiographic image data output from the radiation detector. The radiographic imaging apparatus, which may be either portable or fixed, is being rapidly distributed due to its advantage of enabling immediately verifying an image compared to conventional image plates.
Various types of such radiographic imaging apparatuses have been proposed. For example, an indirect type converts radiation into light in a single operation using a scintillator of, for example, CsI:Tl, GOS (Gd2O2S:Tb), or the like, converts the converted light into electric charges through a semiconductor layer, and then stores the electric charges.
The amount of radiation emitted when the radiographic imaging apparatus is preferably decreased when it is used, for example, in living bodies. A scintillator which emits a great amount of light and has high sensitivity has been desired in the field of optical detector. From that point of view, several radiographic imaging apparatuses were proposed (e.g., Japanese Patent No. 3333278 and Japanese Patent Application Laid-Open (JP-A) No. 2001-330677). Such a radiographic imaging apparatus is constructed by attaching a scintillator, made of crystals of CsI or the like, to an insulating substrate, and emits radiation from an optical detector side.
A CT apparatus having a scintillator having crystals, in which the crystals have a quadrangular pyramidal frustum-shape in view of improving uniformity of light emission, was also proposed (for example, see JP-A No. 2004-125722).
A preparation of a radiation image conversion panel in which a column diameter of a columnar crystal is made larger by improving a degree of vacuum and increasing a temperature of a substrate during forming a scintillator layer was also proposed (for example, see JP-A No. 2004-233343).